If the glasses are so heavy that they're going to sink your nose into the nasal cavity, then I could understand going with plastic. Mine are -4.25 -50 x130 (right) and -3.75 -50 x035 (left) [sphere, cylinder, axis]. I have tried various plastic lenses several times, and what has driven me crazy is not chromatic aberration so much as the distortion at the edge of the visual field, which I find particularly disturbing when driving, especially at night. It's getting harder to find glass lenses, but I do note a Canadian company that still has high index ultra thin glass lenses that should work well in cases of extreme myopia: http://www.visionsofcanada.com/csi/awb/voc/high-myopia.asp. A separate problem is that the opticians tend to try and sell smaller lenses in glass, since they worry about the weight, and, unfortunately, when one is used to gigantic lenses, a shift in lens size can create difficulty in adjusting. I find myself still reverting to a 1996 pair of no-line trifocals with PhotoGray in Flexon frames--the best pair I ever had, also, coincidentally, the heaviest, and with the largest lenses. Opticians seem to have no understanding of physics as they try to "convert" me to the plastic religion.

if you read the original article and some of the follow-up, you'll see that manufacturers play with numbers to make things look really good.

the three horsepower claim is most likely what is described as 'peak' hp - not much relationship to actual use.

'modern day' kitchens typically have 20 amp circuits in the kitchen, older homes perhaps 15 amps. you can figure the available wattage from there - something advertised as 3500 watts sounds good, but probably will trip breakers under (heavier) load.

Can you work out the RPM of blenders from their wattage?
I'm thinking of the Ninja Nutri Blender QB3000NZ (132515) at 700Watts,
as against the Ninja Nutri Blender BL450(NZ) at 900 Watts.
I do understand there is a reduction in speed under load, and that bowl size also makes a difference, but thought average rpm might give a clue to
how fast they really are?
Thank you

I know I'm quite late to the party here, but I just posted an article discussing Vitamix horsepower that I thought you might be interested in. I measured input and output power (peak and sub-peak), and also wrote about how the power depends on what you are blending.

It depends on what you mean by "the power of a blender." What I meant when I said "the power depends on what you are blending," is that both the input and output power depend on what is being blended. I am 100% certain of that.

If you take "power of a blender" to mean its peak power, then sure, that is an inherent property of the blender. (However, peak power is defined by a certain load...)

RPM is important, but I wouldn't use it as the main means to compare blenders. There isn't a standard for what manufacturers actually mean when they give you an RPM number. Sometimes it's a "bare motor" speed (which is the maximum speed of the motor, if it weren't connected to anything), and other times it's an actual operating speed. And even then, the RPM usually depends on what you are blending.

All that said, 3,000 RPM sounds super low for a 1200W blender. I think it's either a typo, or a different kind of machine.